With the raise of the Long Term Evolution-Advanced (LTE-A) demands, people pay more attention to node average spectral efficiency and node edge spectral efficiency. Comparatively speaking, the node edge spectral efficiency attracts the most attention, it is chiefly because both uplink and downlink of an LTE-A system are frequency division systems with Orthogonal Frequency Division Multiplexing (OFDM) or certain transformations of OFDM as a basic multiple access mode, which is different from a traditional wireless communication system with Code Division Multiple Access (CDMA) as the basic multiple access mode. The LTE-A system does not have processing gain, and due to complete orthogonal frequency division, there are few interference problems within the nodes, but interference processing at the edge of the nodes is relatively difficult.
In the LTE R8/9/10 (release 8), the interference processing at the node edge mainly includes the following three ways: 1. interference randomization; 2. interference elimination; 3. interference coordination (avoidance). In the interference randomization, generally ways such as frequency hopping, time hopping, direct spread or code hopping are adopted to mitigate the influence of interference between the nodes, an advantage therefore is that no network planning is required and support of signaling is hardly needed, however, it only means that the interference is alleviated but not eliminated fundamentally; in the interference elimination, though the interference can be eliminated with certain algorithms, generally additional physical entities such as the multi-antenna technology are required to better eliminate the interference, sometimes these conditions may not be satisfied in practical applications; the last way, interference coordination (avoidance), is to, by exchanging some information between nodes, make each node automatically select appropriate resources for transmission according to feedback information of other nodes and its own conditions by using certain algorithms, thereby implementing efficient utilization of inter-node resources, and reducing chances of resource utilization collision between nodes to the greatest extent, and eventually achieving an enhancement of the node edge performance, which stresses trying to avoid an interference resulted from contention of the same time-frequency resource between the nodes. Moreover, since distances between node edge users and antennas of multiple adjacent nodes do not vary much, the achievement of higher capacity and reliable transmission of wireless links at the edges of the nodes by using transmitting antennas of the multiple nodes becomes a research emphasis.
In order to further improve the edge spectral efficiency and meanwhile improve the cell average spectral efficiency, in the LTE R11, the Coordinated Multiple Points Transmission/Reception (CoMP) technology is introduced, and the introduction of the CoMP technology mainly includes three types of transmission modes: Dynamic Point Selection/Dynamic Point Blanking (DPS/DPB), Joint Transmission (JT) and Coordinated Scheduling/Coordinated Beamforming (CS/CB).
In the DPS/DPB transmission mode, a network side dynamically selects a best node to perform data transmission to a terminal according to channel characteristics of different nodes and the terminal; meanwhile other nodes can dynamically choose whether to keep muting or not according to interference conditions. In the JT mode, according to interference conditions of different nodes and the terminal and service load conditions of the different nodes, multiple nodes can be selected to serve the terminal jointly, thereby changing interference signals into useful signals. The CS/CB mode is mainly to try to avoid beam collision on same resources for different nodes by scheduling.
In the CoMP related art, in order to support the selection of a coordinated node by a sending part and the determination of a Modulation and Coding Scheme (MCS), the network side will configure multiple non-zero power Channel State Information Reference Signal (CSI-RS) resource sets for the terminal through a UE-specific Radio Resource Control (RRC) signaling, these multiple CSI-RS resource sets are called CoMP measurement sets, and the terminal will measure the multiple non-zero power CSI-RS resource sets, which is used for performing CSI feedback. Meanwhile, in generally speaking, the transmission nodes serving the terminal are within a range of transmission nodes corresponding to the multiple CSI-RS resource sets. Moreover, in order to support the demand of Reference Signal Receiving Power (RSRP) measurement in a specific scenario, the network side will also configure multiple non-zero power CSI-RS resource sets through the RRC signaling, and these multiple non-zero power CSI-RS resource sets used for the RSRP measurement are called CoMP resource management sets.
In the LTE R8/9/10, different types of signals are all sent from the same node, thus channel large-scale characteristics that can be obtained by estimation based on any signal are used for calibrating other signals.
However, after introducing CoMP technology or distributed antennas technology, since physical locations of different antennas for transmitting signals are mutually separated, and different signals are probably from different transmission nodes or transmitting antennas in separated physical locations, the channel large-scale application mode in the LTE R8/9/10 will cause an error in the R11, thereby influencing channel estimation precision and signal detection precision.
Moreover, in the LTE R11, in order to further improve a capability of the control channel, particularly with respect to a channel capacity in a case that multiple nodes share a cell ID, and meanwhile in order to improve a coverage distance of the control channel, an enhanced control channel based on demodulation reference signals is introduced, in the transmission of the enhanced control channel, since detection of the control channel is based on the demodulation reference signals, and configuration of the demodulation reference signals is UE-specific, transmitting nodes/antennas of the enhanced control channel may also be different from transmitting nodes/antennas of other signals/channels/reference signals. If continuing to follow the way of R8/9/10, it will also cause a detection performance reduction due to the inaccurate synchronization precision and channel large-scale parameter estimation.